Reversible structural transformation of FeOxnanostructures on Pt under cycling redox conditions and its effect on oxidation catalysis

Abstract

Understanding dynamic changes of catalytically active nanostructures under reaction conditions is a pivotal challenge in catalysis research, which has been extensively addressed in metal nanoparticles but is less explored in supported oxide nanocatalysts. Here, structural changes of iron oxide (FeO_x) nanostructures supported on Pt in a gaseous environment were examined by scanning tunneling microscopy, ambient pressure X-ray photoelectron spectroscopy, and in situ X-ray absorption spectroscopy using both model systems and real catalysts. O–Fe (FeO) bilayer nanostructures can be stabilized on Pt surfaces in reductive environments such as vacuum conditions and H₂-rich reaction gas, which are highly active for low temperature CO oxidation. In contrast, exposure to H₂-free oxidative gases produces a less active O–Fe–O (FeO₂) trilayer structure. Reversible transformation between the FeO bilayer and FeO₂ trilayer structures can be achieved under alternating reduction and oxidation conditions, leading to oscillation in the catalytic oxidation performance.